Electrostatic telephonic instrument for transmitting or receiving purposes



Dec. 7 1926.

J. MASSOLLE ELECTROSTATIC TELEPHONIC INSTRUMENT FOR TRANSMITTING OR RECEIVING PURPOSES Filed August :5. 192.5

Patented Dec. 7, 1926. I v

UNITED STATES' JOSEPH MASSOLLE, OIE' k.A.G'., 0E ZURICH, SWITZERLAND, A

ELECTROSTATIC TELETHONIC INSTRUMENT FOR TRANSMITTING PURPOSES.

This invention relates to improved electrostatic telephonie instruments for transmitting or receiving purposes and more particularly or preferably to a so-called loudspeaking receiver..

It is a known fact t-hat'a perfectly true sound reproduction free from disturbing resonance notes and distortionsor deformations cannot be obtained in a satisfactory manner except by means of apparatus which work on the electrostatic principle. -In contradistinction:thereto all of the apparatusI which at ,present are usually practised and in which the alternating currents are transformed into'sound waves according to the `electromagnetic principle, are very objectionable. The reason of the superiority of the apparatusworking on the electrostatic principle resides in that heavy and strong iron diaphragmsneed notbeemployed therein and, as contrasted with magnetic loud-spcaking receivers, funnel-shaped amplifying lioins are not required in order to ensure a coupling with a quantity of air sufficient to realize a loud sound reproduction. For

electrostatic loud-speaking receivers of `the` kind. as is well known in the art` allow of employing or applying larger surfaces so that such surfaces are sufficiently coupled with the air.

An object of this invention is to improve the electrostatic instruments for transmit- -ting or receiving purposes, particularly loudspcaking' receivers having tightly stretched diaphragms, as hitherto constructed, by stretching the latter into theirefficient position and holding the same in such position by means of the capacity body. or in other words,- by positively forcing the capacity body mounted on the diaphragm holder, towards the diaphragm and securing the body inthe holder with the diaphragm in v properly stretched position. Other objects of the inventionvconsist in the provision of improved forms of construction and combinations of elements, all as will more fully appear in the following specification.

diaphragm.

BERLIN-WILMERSDORF, GER-MANY, ASSIGNOR TO 'IRI-ERGON,

CORPORATION OF SWITZERIJAND. f

hBECEIVING An electrostatic instrument constructed according to the present invention, therefore, mainly comprises a rigid capacity body, a

ISSUED Application led August 3, 1925, Serial No. 47,662, andin Germany July 9, 1925.

very thin diaphragm or film in front of the former and a short distance apart therefrom only, and a diaphragm holder, the two faces of the diaphragm or film being absolutely plane and parallel to each other and one face being coated with an electric conductor as usually. i

In practically using an electrostatic instrument especially loud-speaking receiver of the improved construction the alternat? ing voltages lie between the electric conl ductor orl coating of the diaphragm and the capacity body. The variation of voltage results in a variationof thel electrostatic forces of attraction between diaphragm and capacity body. The diaphragm vibrates according to the rhythml of the alternating voltages andV produces in this way corresponding sound waves. y

According to the present invention the diaphragm preferably consists of an eX- tremely thin mica film with a metallic coat-,

ing'thereon vand the holderpreferably con-- sists of two rings adapted to be firmly connected to cach other with the diaphragm interposed therebetween so as to be perfectly plane. The two rings constituting the diaphragm holder are connected with each other by means .of screws or the like and they are shaped-in section-in a manner that., upon tightening the screws, the diaphragm periphcrally interposed between the two halves'.

of the holder, will receive a preliminary stretching in radial respects so that the same will be perfectly flat and plane.

Thethus obtained preliminary stretching of the diaphragm is efficiently completed preferably in the following way. The rigid capacity body is provided With a contacting member or surface co-operating With-thefilm'or diaphragm and situated sufiiciently remote from or. above the active surface of the capacity body to cause the diaphragm, upon tightening the screws provided for connecting the capacity body to the holder to be displaced from its previous at condition or plane without changing or interfering with the requisite distance between the inner face of the diaphragm and the opposed face of the capacity body or with the parallelism of the active surfacey of the latter and the diaphragm. In other words, by connecting the improved capacity body with the bipartite holder by means of screws a means will be afforded for giving the diaphragm the requisite stretching and tension by displacing the same with respect to t-he holder'but without displacing the same with relation t the capacity body.

With the above vrecited and other objects inY View, the invention resides in the novel construction set forth in the following specification, particularly pointed out in the appended claims and illustrated in the acc0mpanying drawings, it being understood that the right is reserved to embodiments other than those actually illustrated herein to the tion; l igure 2 being full extent indicated by the general meaning of the Yterms 1n whlch the claims Vare ex pressed,

In the accompanying drawings forming a part of this specification a single example or embodiment of' the invention is exhibited, Figure 1 being a View in axial. or central scction of the diaphragm holder with the diaphragm clamped, etween the two parts thereof in its preliminary'stretched posia similar sectional View of the capacity body; and Figure 3 showing the two components illustrated in Figures 1 and 2, duly assembled and with the diaphragm in fully tensioned condition.

Referring to Figure l the thin mica film 1 is providedon its outer face with an electrically conducting, preferably metallic coating 2 and the periphery of the diaphragm is clamped between the two rings 3' and. 4 which constitute the holder, these rings l being of like dimensions in diametrical respects. The inner edge 5 of the'inner periphery of the ring3 is rounded, whilst the lnner edge of the outer periphery of the ring 3 is shaped to form an annular flange 11. The two rings 3 and 4 are to be connected with each other, in superposed relation and with the peripheral portion of the diaphragm 1 therebetween, by means of screws 6. By tightening the latter the two ringls will ap to t e particular shape of the ring 3 and the springiness ensured such shape, the diaphragm 1 will be'r ially drawn outwards and thereby receive a preliminary stretching 'to form an accurately plane surface as shown in Figure 1.

The circularl or disk-shaped capacity body.

comprises a central portion 19, a peripheral or rim portion 8 and an intermediate portion 7 which is thoroughly plane on both sides and of even tlnclmess throughout.

Ythe holes in the flange 10 roach each other and, owing- The three portions constituting the capacity body are preferably made in one piece so as to be integral with each other. The rim 8 comprises a main portion 9 which is of the same thickness, in axial regards, as the een tral portion ,19, and an Y'annular flange 10 projecting from the portion 9 outwards or in radial directions so that the' two parts 9 and 10 are perpendicular to each other. Thel annular flange 10 is provided with a number of holes and insulating bushes 12 of non-conducting material are inserted into the holesY for the reception of screws 13. l

The ring 4 of the diaphragm holder is provided with screw-threaded holes or openings 14 corresponding in number and location to of the capacity body, so that the latter can be firmly connected with the holder by means of the screws 13 passing through the bushes 12 and into the threaded holes 14 of the holder, as will be clearly understood on inspection ot' Figure 3.

The central portion 19 of the .capacity body is cup-shaped toaccommodate an annular disk 1? filling the cup to the level of the intermediate portion 7 of the body, and the bottom of the cup is enlarged to form a boss 20 with a central threaded bore for the reception of a short spindle or screw 18 the purpose ofrwhich will be explained further below. l i y On the top of the described capacity body two flat'rings 15 and 16 made of ainon-conducting material such as pap'er or the like, are placed, the larger ring 15 being supported by the -portion 9 of the rim 8 and the narrower ring 16 being supported by the disk 17 which fits loosely in the cup or cavity of the central portion 19 of the capacity body. i

The dimensions of the ring 4 of the holder and ot the portion 9 of the rim 8 of the capacity body are selected to render the distance a, Figure 1, between the lower or inner surface of the mica diaphragm andthe edge 14 ofthe ring 4 somewhat less than thc4 distance b, Figure 2, between the top of the bushes 12 and the plane of or coinciding with the upper faces of the paper or other insulating rings 15 and 16, so that upon assembling and connecting together the holder and the capacity body `by means of' .out of its position, shown inv Figure 1. into a parallel plane, as shown in Figure 3. In this way the requisite tension of the daphragm is brought about and the paper rings 15 and 16 act to prevent the properly stretched. .and tensioned diaphragm from contacting with the intermediate portion 7 of the capacity body, when caused to vibrate. The extent to which the diaphragm 1 is removed or lifted from the plane posii ace of the capacity body in the cup or cavity of the i,leoe,veo

tion shown in Fig. 1 to the elevated position illustrated in Figure 3, that is, the stretching or final tension of the diaphragm, there-l fore, is determined by-the difference between the dimensional values aand b, Figures 1 and 2.

For the purpose of adjusting the diahragm 1 with relation to the opposed sur- I provide the disk 17 fitting loosely central portion 19 of the capacity body, and the spindle or screw 18, as hereinbefore described. .By means of the spindle or screw 18 the disk 17 can be raised above the level or plane of the intermediate portion 7 of the v capacity body whereby the paper ring 16 kphragm is made or consists.

be lifted'out of the plane of the paper ring 15 and the diaphragm 1 correspondingly s aced -apart from the capacity body tothe esired or required extent.

In order to maintain the tension ot the diaphragm, obtained in the manner hereinbefore described, constant for any length oftime, it is advisable to use a materialfor making the two clamping rings 3 and 4, which ossesses' the very same coelicient of expansion as the material of which the dia'- Thus if the diaphragm consists of mica, clamping rings 3 and 4 made of suitable cast iron will give satisfactory results on the line above indicated, it being possible to reduce, .by select ing a cast iron of the required properties, the difference between the coeicients of expansion of the two materials, viz, mica and will vcast iron, so far as to realize and ensure a.l p

radially outwards to the rear of tension in the diaphragm which is practically constant or-independent of variations ofpeo in said temperature.

The intermediate'portion 7 of the capacity body ina be provided with perforations 21 pre erably arranged symmetrically all over the annular portion 7, for the purpose of reducing the damping in the between the diaphragm and the capacity body.

What I claim isz- A.

l. In an electrostatic telephone, the com-- bination of a diaphragmholder, a' daphragm, in said holder, capacity body and means for securing 4sai plate to said holder, after said diaphragm a rigid plate constitutinga is secured in saidv holder, in such position that said plate will exert pressure against said diaphragm, within Ysaid holder, to stretch the diaphragm.

2. In an electrostatic telephone, the combination of a diaphragm holder, a diaphragm means for securing said diaphragm holder, 'a rigid plate constituting a capacity body having a pressure Adevice associated therewith, and means for securing-saidplate 'rigidly to said holder, afterl spacing means on means for securing said diaphragm -said diaphragm is secured in' said holder,`

such position thatsaid pressure device will bear against said 'dia hragm, vwithin said holder, to displace it in the plane occupiedthereby previous 3.A In Aan electrostatic telephone, the conibiiiation of a air of rings'constituting' a diaphragm hol er, a diaphragm, means for securing the same rigid plate constituting a capacity carrying a pressure to the securing of. said, plate in position, to stretch the diaphragm.

between said ringd a device, and having an offset outer flange, and means for securing a capacity body, having'a forward face v and a rearwardly extending marginal flange with an outwardlyextending ,oiset ortioii,

spacing .means to be ppsitioned etween said forward face and said diaphragm, `and means for securing said iange oiset portion against one of said rings with said 's acing means bearing against said diap raum to stretch the same.

5. In an electrostatic telephone, thecombination of one unit comprising a diaphragm and rigid ring secured to-the edge thereof,

a second unit comprising a rigid condeiser exten ing late and seating means therefor said plate,

and rigidly connected thereto, and means for securing said seating means against said ring with against said diaphragm within said ring to stretch the same.

6. In an electrostatic telephone, the combination of a unit comprising a diaphragm and rigid ring secured to the edge thereof, a rigid condenserplate, seating means therefor rigidly connected thereto and extending radially outwards to the rear thereof, the-edge and center of and means for securing said seatsaid plate,

anst said ring with said plate ing means ag d extending within said ring and said s acng means exerting pressure `against sai phra to stretch the same.

7. n an electrostatic telephone, thev combination of a holder, a diaphragm having its edge secured thereto, a rigid condenser plate, seating means therefor rigidlyv connected thereto and extending racially outwards to the rear thereof, spacing means extending through saidvplate and adapted to Abe positioned atan ad]usted distance beyond the faceof said plate, and means for securing said seating means against said said plate exerting pressure .gig .1,609,760

holder with said plate extending within said tension, a rigid condenser plate, rearwardly holder and exertin pressure against said spaced marginal seating means therefor, 10

diaphragm to stretc the same. and means for securing said seating means 8. In an electrostatic telephone, the comagainst one of said rings with said plate 5 bination of a holder comprising a pair of exerting pressure against said diaphragm rings, and a diaphragm secured at its edge to place the same under tension greater between the same, said rings being arranged than said preliminary tension. to place said diaphragm'under preliminary JOSEPH MASSOLLE. 

